1. Field of the Invention
The present invention relates to a mold clamping apparatus for use in an injection molding machine, and more particularly to a spindle driving device in a mold clamping apparatus, which is low in cost and has an improved responsiveness.
2. Description of the Related Art
In injection molding machines, mold clamping apparatus have been known of a type comprising a drive source consisting of an electric motor (hereinafter referred to as a motor), and a power transmission system for converting a turning force generated by the drive source into a driving force for axially driving a spindle, and wherein a movable platen arranged to be movable in unison with the spindle is axially driven by the drive source through the power transmission system so as to perform mold-opening, mold-closing and mold-clamping. In a mold clamping apparatus of this kind, the drive source may consist of a single general-purpose motor capable of generating a required mold clamping force of from 5 to 10 tons in case of a small or medium apparatus. In a large mold clamping apparatus requiring a larger mold clamping force, however, the drive source must be of a specially ordered high-output type. For this reason, a considerable cost increase occurs and further operational responsiveness of the motor deteriorates since the inertia of the rotor becomes large.